Sandbox10

'''This sandbox is in use until June 1, 2009 for UMass Chemistry 490a. Others please do not edit this page. Thanks! Brendan Jones'''

Myosin 2 Motor Domain
Myosin is a protein known largely for it's involvement in the contraction of the body's muscles. However, this protein can also be found in the ears and eyes, blood platelets, and it has functions in cytokinesis.

Myosin II is found in the myofibers of skeletal, smooth, and cardiac muscle tissue where the protein forms the thick filaments. The myosin of the thick filaments has the ability to bind the thin filaments, composed of actin. The myosin head then rotates and pulls the two filaments past one another providing the basis for muscle contraction.

The portion of the protein that is shown is the motor domain of the heavy chain. This protein is largely composed of alpha-helices connected by randomly oriented chains. There are also several areas of beta-sheets, both parallel and anti-parallel. This component of the protein represents only one part of the hexamer the makes up the entire mosin unit. In addition there is another heavy chain and four light chains. The tails of the two heavy chains, which can not be seen, coil about one another to form the thick filament. The four lights chains bind the myosin between the head and tail region, two light chain molecules per heavy chain. These light chains are known as the essential light chain and the regulatory light chain.

This view shows the active sites of the protein with the ATP analog ADP-Metavanadate bound to one active site and the allosteric inhibitor pentabromopseudilin.

Myosin contains many polar side chains on the surface of the protein, but there are also a large number of nonpolar molecules on the surface. The following scene shows a contrast between hydrophobic (gray) and hydrophilic molecules on the surface of the protein in a space-filling view and a cartoon view. By looking at these scenes one can see that although hyrbrophobic molecules penetrate the surface of the molecule, there are no areas of high hydrophobic concentration. Certain secondardy structures of the proteins can form in a way that places hydrophobic residues on the surface and hydrophobic residues in the interior. The alpha helix and beta sheet highlighted in these scenes shows the alternating pattern between hydrophilic and hydrophobic residues. The repetition is not perfect, but the majority of the residues are in their favored environment.

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Thanks to Fedorov, R., Boehl, M.,  Tsiavaliaris, G.,  Hartmann, F.K.,  Baruch, P.,  Brenner, B.,  Martin, R.,  Knoelker, H.J.,  Gutzeit, H.O.,  Manstein, D.J. for their work in resolving the structure of this protein.